1. Field of the Invention
This invention generally relates to wireless communications antennas and, more particularly, to a dual telescopic whip antenna that is especially useful with small portable wireless communication devices.
2. Description of the Related Art
The size of portable wireless communications devices, such as telephones, continues to shrink, even as more functionality is added. As a result, the designers must increase the performance of components or device subsystems while reducing their size, or placing these components in less desirable locations. One such critical component is the wireless communications antenna. This antenna may be connected to a telephone transceiver, for example, or a global positioning system (GPS) receiver.
One antenna design is the patch antenna, which can be incorporated into a wireless device circuit board or the device chassis. However, the close proximity of the chassis to the user can limit the performance of such an antenna. Typically, better communication results are achieved using a whip antenna. Using a wireless telephone as an example, it is typical to use a combination of a helical and a whip antenna. In the standby mode with the whip antenna withdrawn, the wireless device uses the stubby, lower gain helical coil to maintain control channel communications. When a traffic channel is initiated (the phone rings), the user has the option of extending the higher gain whip antenna. Some devices combine the helical and whip antennas. Other devices disconnect the helical antenna when the whip antenna is extended.
The whip antenna has a physical length, when extended, related to the antenna operating frequency. When withdrawn, the whip antenna must fit within the constraints of the wireless device chassis. Therefore, as the wireless device chassis decreases in size, the extended length of conventional whip antennas has necessarily decreased. A shorter whip antenna can be made to operate at the same frequency as longer whip antennas by using higher dielectric constant materials in the antenna fabrication. However, the use of higher dielectric constants makes for a lower gain antenna, and a poorer performing wireless device.
One popular solution to the above-mentioned length problem has been to fabricate the whip antenna as a wire with a telescoping tube section. When the antenna is withdrawn, the wire section is withdrawn into the tube, with the tube being withdrawn into the chassis. When extended, the combination of the wire and tube section define the antenna length.
As mentioned above, one advantage of the whip antenna is a reduced proximity to the human user, who blocks the signal path around the antenna. Whip antenna performance can be further enhanced by further reducing the proximity of the antenna to the user. Safety is another reason for reducing proximity, as there is concern that the proximity of the human head to wireless transmissions may be a health hazard. For these reasons it is desirable to angle the whip antenna from the device chassis when extended, away from the user. When withdrawn, such an angled antenna would necessarily reside in a channel formed through the center of the device chassis (where the electronic components reside), unless the withdrawn antenna can be bent. However, the relatively rigid telescoping tube is not completely flexible. Further, a truly flexible telescoping tube would be easily damaged when the phone is accidentally dropped.
It would be advantageous if a high performance whip antenna could be withdrawn into a compact length using more than one telescoping section.
It would be advantageous if a telescoping whip antenna could be angled away from the device chassis when extended.
The present invention describes a dual telescope whip antenna. Since two telescoping tubes are used, having approximately half the length of a conventional single tube design, the antenna can be extended at an angle with respect to its withdrawn (contracted) position. That is, the shorter tubes can be inserted into the chassis collection channel at an angle. The antenna has a physical length that is not limited to the chassis collection channel length, or the angle between the antenna withdrawn and extended orientations.
Accordingly, a dual telescopic whip antenna is provided. The antenna comprises a radiator including a conductive wire, and a first telescoping tube section having a first end to accept the wire and an antenna port at a second end. The radiator also includes a second telescoping tube section having a first end to accept the other end of the wire. The radiator has an extended position length that is approximately equal to the sum of the wire length, the first tube length, and the second tube length. The radiator has a contracted position with the wire length substantially withdrawn in the first and second tubes.
In some aspects the antenna further comprises a chassis with a stopper channel assembly to accept the first and second tubes in the radiator contracted position and to limit the extension of the first tube from the chassis in the radiator extended position. The stopper channel assembly also includes a transmission line terminal that is connected to the antenna port in the radiator extended position.
Additional details of the above-described antenna, a wireless communications device dual telescopic antenna system, and a dual telescopic antenna method are described below.